In a hot-rolling mill or thin slab casting and rolling TSCR, especially an Arvedi-ESP thin slab casting and rolling TCSR, a hot metal band can be produced in a multiplicity of ways:
In the so-called batch mode, a slab is rolled in at least one roll train, forming a finished band. The finished band is cooled in a cooling zone and then wound up by means of a winding device, forming coils.
In the so-called semi-endless mode, an endless strand is pre-rolled in a first roll train, forming an intermediate band with a thickness of 15 mm. The intermediate band is split up by means of shears, finally rolled in a second roll train, forming a finished band with final thicknesses of 3.5 mm, then cooled in a cooling zone and after that wound up by means of one or more winding devices, forming coils. The speeds of the finished hot band are approximately 3 m/s maximum in this case, depending on the final thickness. With this relationship of minimum final thickness and maximum band speed, the band heads can be stably transported over the roller table toward the winding device.
In the so-called endless mode, an endlessly cast strand is rolled in a first and second roll train, the finished band is cooled in a cooling zone and after that it is wound up in a winding device, forming coils. The resulting hot band is split into suitable lengths by so-called flying shears located immediately upstream of the winding device and wound in an alternating manner on the winding devices, forming steel coils. With this method, hot bands with final thicknesses of between 0.6 and 6 mm are produced. These hot bands can have a maximum speed of 17 m/s, depending on the final thickness.
In the endless mode, after cutting, the band heads are transported over roller tables to one of the two winding plants, optionally to a third winding plant, where the winding up takes place. In the process, the band heads also run through the winding driver. Since bands in a lower thickness range (up to 0.6 mm) have only a very low rigidity, during their forward movement, the band heads can be bent up in the event of sudden contact impact with the transporting rollers. After this time point, as a consequence of the altered inflow conditions and pressure conditions between the upper and lower sides of the band head, strong lift forces occur, which depend on the inflow speed and the angle between the band head and the horizontal. The gravity force of the bent up band section acts in opposition to the lift forces (see FIG. 1). If the lift force is greater than the gravity force, then the band head lifts away from the roller table. The movement of the band becomes unstable, the band begins to “fly” and possibly folds back (see FIGS. 2a to 2c). These occurrences lead to a loss of quality of the bands and can also lead to a so-called “cobble” with mill shutdown.